1. Field of the Invention
This invention relates generally to digital cameras and, more particularly, to a digital camera for recording image data onto an unloadably loaded recording medium, such as a memory card or optical disk, and reproducing record data out of the recording medium.
2. Description of the Prior Art
The digital cameras have functions of reproducing compressed image data out of a recording medium and decompressing it into a decompressed image to be displayed on a monitor provided thereon. Some of the digital cameras have also a function of reproducing sound data out of a medium as above and outputting it via a speaker through predetermined signal processing.
Meanwhile, the parameters associated with the reproduced image and sound data vary in quality. The individual image sensors are quite different in respect of the parameter of resolution, e.g., pixel count ranges from as low as about 0.35 million to as high as nearly several hundreds of millions. In order to actually display reproduced images on a monitor, encoding has to be done so that the resolution can be matched to the image sensor. In dealing with motion image data, not only the quality of the resolution parameter but also the quality of the frame rate parameter should be taken into consideration. For motion image data, in some cases 15 still images constitute 1 second of motion image whereas in other cases 30 still images are required for 1 second of motion image. For proper speed reproduction, reproduction should be suited in frame rate. Furthermore, for reproducing sound data, the quality associated with this parameter, which may be expressed in terms of sampling rate or quantization bit count for conversion from an analog to digital signal, must be taken into account.
In this manner, the qualities of different digital cameras are greatly different from one to another in respect of resolution, frame rate, sound quality, and other parameters. However, as long as the still image, motion image or sound having been taken by one person's digital camera is reproduced on that camera, it is satisfactory to merely have a corresponding reproduce function to a recording function of the same camera.
However, today's digital cameras employ unloadable recording media, such as memory cards and magneto-optical disks. It is possible to commonly utilize only one recording medium between the digital cameras adopting a same scheme of recording media. This means that one can use on his or her digital camera a recording medium having been used on another's digital camera. However, if there is superiority or inferiority in parameter quality between these cameras, the data recorded by the digital camera implementing the superior parameter quality is impossible to reproduce on a digital camera implementing on inferior parameter quality. More specifically, if one digital camera has an image sensor with a resolution quality of XGA and the other digital camera has that of VGA, image data with XGA taken by the one digital camera cannot be reproduced on the other digital camera having no XGA-compatible encoding function.